Israeli law enforcement officials say they want to question Lev Leviev, the business baron whose companies allegedly are at the center of a vast diamond-smuggling ring that has operated for years, Haaretz reported.

Among six people the police detained for questioning Monday are two of Leviev’s relatives and four people who are or have been involved in his companies in Israel and Russia. The police have asked a court to extend the detention of the six suspects, said the Haaretz report.

A source close to the Uzbekistan-born Leviev said he might return to Israel voluntarily for questioning, the Haaretz report said.